Generally speaking, a direct current (DC) conversion circuit is disposed with an energy storage element. The inductance value of the energy storage element affects the response speed of the input current and the output voltage ripple in the DC conversion circuit. If the inductance value of the energy storage element is relatively smaller, the response speed of the input current of the DC conversion circuit is relatively faster, but the output voltage ripple is relatively larger. On the contrary, if the inductance value of the energy storage element is relatively larger, the response speed of the input current of the DC conversion circuit is relatively slower, but the output voltage ripple is relatively smaller.
Therefore, for general DC conversion circuits, usually inductors with relatively smaller inductance values and capacitors with relatively larger capacitance value are employed. In other words, the energy storage element with a relatively smaller inductance value and a relatively larger capacitance value is employed. Thus, the DC conversion circuit can have a relatively faster response speed of the input current and a relatively smaller output current ripple. Furthermore, an electrolytic capacitor is usually employed as the capacitor with a relatively larger capacitance value, so as to achieve the relatively faster response speed and the relatively smaller output current ripple.
However, because an electrolytic capacitor is easily affected by external circumstances and factors such as the operation of switch and temperature, the electrolytic capacitor has a shorter life expectancy than other types of capacitors made of different materials. As a result, the life expectancy of the DC conversion circuit is also shortened.